US20200079951A1

US20200079951A1 - Thermoplastic Resin Composition and Molded Article Manufactured Therefrom

Info

Publication number: US20200079951A1
Application number: US16/466,346
Authority: US
Inventors: Yun Jeong YANG
Original assignee: Lotte Chemical Corp
Current assignee: Lotte Chemical Corp
Priority date: 2016-12-27
Filing date: 2017-12-19
Publication date: 2020-03-12
Also published as: KR20180075803A; CN110114404A; EP3564309A4; CN110114404B; JP2020503399A; US11124643B2; EP3564309A1; KR101961994B1; WO2018124594A1; EP3564309B1

Abstract

A thermoplastic resin composition of the present invention is characterized by comprising: a thermoplastic resin containing an acrylate-based rubber-modified vinyl-based graft copolymer and an aromatic vinyl-based copolymer resin; an ultraviolet stabilizer containing a hindered amine light stabilizer (HALS)-based ultraviolet stabilizer and a benzotriazole-based ultraviolet stabilizer; and zinc oxide having an average particle size of about 0.5 to about 3 μm and a specific surface area BET of about 1 to about 10 m2/g. The thermoplastic resin composition has excellent weather resistance and antibacterial properties.

Description

TECHNICAL FIELD

The present invention relates to a thermoplastic resin composition and a molded article manufactured therefrom. More particularly, the present invention relates to a thermoplastic resin composition that exhibits good properties in terms of weather resistance, antibacterial properties, and the like, and a molded article manufactured therefrom.

BACKGROUND ART

An acrylate-based rubber-modified aromatic vinyl copolymer resin such as an acrylonitrile-styrene-acrylonitrile copolymer resin (ASA resin) has better weather resistance (discoloration resistance) than a diene-based rubber-modified aromatic vinyl copolymer resin such as an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) and is used for interior/exterior materials for electric/electronic products and automobiles, exterior materials for buildings, and the like, which require weather resistance.
However, since use of such an acrylate-based rubber-modified aromatic vinyl copolymer resin alone has a limitation in improvement of weather resistance (discoloration resistance), a weather stabilizer such as a UV stabilizer is added to achieve a desired degree of weather resistance. However, since an excess of the weather stabilizer can cause deterioration in external appearance and mechanical properties due to out-gassing, increase in amount of the weather stabilizer is not preferred.
Moreover, a molded article produced from a thermoplastic resin is required to have antibacterial properties when used for application entailing direct or indirect body contact.
Therefore, there is a need for development of a thermoplastic resin composition exhibiting good properties in terms of weather resistance, antibacterial properties, and the like without deterioration in properties of a thermoplastic resin.
The background technique of the present invention is disclosed in Korean Patent No. 1452020 and the like.

DISCLOSURE

Technical Problem

It is one object of the present invention to provide a thermoplastic resin composition exhibiting good properties in terms of weather resistance, antibacterial properties, and the like.
It is another object of the present invention to provide a molded article formed of the thermoplastic resin composition.
The above and other objects of the present invention can be achieved by the present invention described below.

Technical Solution

One aspect of the present invention relates to a thermoplastic resin composition. The thermoplastic resin composition includes: a thermoplastic resin including an acrylate-based rubber-modified vinyl graft copolymer and an aromatic vinyl copolymer resin; an ultraviolet (UV) stabilizer including an HALS (hindered amine light stabilizer)-based UV stabilizer and a benzotriazole-based UV stabilizer; and zinc oxide having an average particle diameter of about 0.5 μm to about 3 μm and a BET specific surface area of about 1 m²/g to about 10 m²/g.
In one embodiment, the thermoplastic resin composition may include: about 100 parts by weight of the thermoplastic resin including about 20 wt % to about 50 wt % of the acrylate-based rubber-modified vinyl graft copolymer and about 50 wt % to about 80 wt % of the aromatic vinyl copolymer resin; about 0.05 to about 2 parts by weight of the HALS-based UV stabilizer; about 0.05 to about 2 parts by weight of the benzotriazole-based UV stabilizer; and about 0.1 to about 5 parts by weight of the zinc oxide.
In one embodiment, the acrylate-based rubber-modified vinyl graft copolymer may be prepared by graft copolymerization of a monomer mixture comprising an aromatic vinyl monomer and a vinyl cyanide monomer to an acrylate-based rubber polymer.
In one embodiment, the aromatic vinyl copolymer resin may be a polymer of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer.
In one embodiment, the HALS-based UV stabilizer may include at least one selected from among bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and bis(2,2,6,6-tetramethyl-2-piperidyl)sebacate.
In one embodiment, the benzotriazole-based UV stabilizer may include at least one selected from among 2-(2H-benzotriazole-2-yl)-4-(1,2,3,3-tetramethylbutyl)phenol, 2-(2-hydroxy-5-methyl-phenyl)benzotriazole, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, and 2-(5-chloro-2H-benzotriazole-2-yl)-4,6-bis(1,1-dimethylethyl)phenol.
In one embodiment, the zinc oxide may have a peak intensity ratio (B/A) of about 0 to about 1, where A indicates a peak in the wavelength range of 370 nm to 390 nm and B indicates a peak in the wavelength range of 450 nm to 600 nm in photoluminescence measurement.
In one embodiment, the zinc oxide may have a peak position (2θ) in the range of 35° to 37° and a crystallite size of about 1,000 Å to about 2,000 Å, in X-ray diffraction (XRD) analysis, as calculated by Equation 1:
$\begin{matrix} Crystallite size (D) = \frac{K λ}{β \cos θ} & [Equation 1] \end{matrix}$
where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree) of an X-ray diffraction peak, and θ is a peak position degree.
In one embodiment, the HALS-based UV stabilizer and the benzotriazole-based UV stabilizer may be present in a weight ratio (HALS-based UV stabilizer:benzotriazole-based UV stabilizer) of about 1:0.5 to about 1:1.1.
In one embodiment, the UV stabilizer and the zinc oxide may be present in a weight ratio (UV stabilizer:zinc oxide) of about 1:0.5 to about 1:10.
In one embodiment, the thermoplastic resin composition may have a color variation (ΔE) of about 0.5 to about 2.5, as calculated according to Equation 2 based on initial color values (L₀*, a₀*, b₀*) measured on an injection-molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter and color values (L₁*, a₁*, b₁*) of the specimen measured using the colorimeter after testing for 3,000 hours in accordance with ASTM D4459.
Color variation (ΔE)=√{square root over ((ΔL*)²+(Δa*)²+(Δb*)²)} [Equation 2]
where ΔL* is a difference (L₁*−L₀*) between L* values before and after testing, Δa* is a difference (a₁*−a₀*) between a* values before and after testing, and Δb* is a difference (b₁*−b₀*) between b* values before and after testing.
In one embodiment, the thermoplastic resin composition may have an antibacterial activity of about 2 to about 7 against Staphylococcus aureus and an antibacterial activity of about 2 to about 7 against Escherichia coli, as measured on 5 cm×5 cm specimens after inoculation with Staphylococcus aureus and Escherichia coli, respectively, and culturing under conditions of 35° C. and 90% RH for 24 hours in accordance with JIS Z 2801, and calculated according to Equation 3.
Antibacterial activity=log(M1/M2) [Equation 3]
where M1 is the number of bacteria as measured on a blank specimen after incubation for 24 hours and M2 is the number of bacteria as measured on a specimen of the thermoplastic resin composition after incubation for 24 hours.
Another aspect of the present invention relates to a molded article. The molded article may be formed of the thermoplastic resin composition as set forth above.

Advantageous Effects

The present invention provides a thermoplastic resin composition that has good properties in terms of weather resistance, antibacterial properties, and the like, and a molded article formed of the same.

BEST MODE

Hereinafter, embodiments of the present invention will be described in detail.
A thermoplastic resin composition according to the present invention includes (A) a thermoplastic resin including (A1) a rubber-modified vinyl graft copolymer and (A2) an aromatic vinyl copolymer resin; (B) a UV stabilizer including (B1) an HALS (hindered amine light stabilizer) based UV stabilizer and (B2) a benzotriazole-based UV stabilizer; and (C) zinc oxide.
(A) Thermoplastic Resin
According to the present invention, the thermoplastic resin may be an acrylate-based rubber-modified vinyl copolymer resin including the (A1) acrylate-based rubber-modified vinyl graft copolymer and the (A2) aromatic vinyl copolymer resin.
(A1) Acrylate-Based Rubber-Modified Aromatic Vinyl Graft Copolymer
According to one embodiment of the invention, the acrylate-based rubber-modified vinyl graft copolymer serves to improve weather resistance, impact resistance, and chemical resistance of the thermoplastic resin composition, and may be prepared by graft polymerization of a monomer mixture comprising an aromatic vinyl monomer and a vinyl cyanide monomer to an acrylate-based rubber polymer. For example, the acrylate-based rubber-modified vinyl graft copolymer may be prepared by graft polymerization of the monomer mixture comprising the aromatic vinyl monomer and the vinyl cyanide monomer to the acrylate-based rubber polymer, in which the monomer mixture may further include a monomer for imparting processability and heat resistance, as needed. Here, polymerization may be performed by any typical polymerization method, such as emulsion polymerization, suspension polymerization, and the like. In addition, the acrylate-based rubber-modified vinyl graft copolymer may form a core (rubber polymer)-shell (copolymer of the monomer mixture) structure, without being limited thereto.
Examples of the acrylate-based rubber polymer may include an alkyl (meth)acrylate rubber, and a copolymer of an alkyl (meth)acrylate and an aromatic vinyl compound. These may be used alone or as a mixture thereof. For example, the acrylate-based rubber polymer may include a C₂to C₁₀alkyl acrylate rubber, a copolymer of a C₂to C₁₀alkyl acrylate and styrene, and a combination thereof, specifically butyl acrylate rubber, a copolymer of butyl acrylate and styrene, and a combination thereof. Here, the copolymer of the alkyl (meth)acrylate and the aromatic vinyl compound may be prepared by copolymerization of about 70 wt % to about 90 wt % of the alkyl (meth)acrylate and about 10 wt % to about 30 wt % of the aromatic vinyl compound, without being limited thereto.
In some embodiments, the acrylate-based rubber polymer (rubber particles) may have an average particle diameter (Z-average) of about 0.1 μm to about 0.5 μm, for example, about 0.15 μm to about 0.4 μm. Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, impact resistance, chemical resistance, and the like.
In some embodiments, the acrylate-based rubber polymer may be a mixture of acrylate-based rubber polymers having different average particle diameters. For example, the acrylate-based rubber polymer may be a mixture of about 40 wt % to about 80 wt % of a first acrylate-based rubber polymer having an average particle diameter of about 0.1 μm to about 0.2 μm and about 20 wt % to about 60 wt % of a second acrylate-based rubber polymer having an average particle diameter of greater than about 0.2 μm to about 0.5 μm or less, in which the mixture of the first and second acrylate-based rubber polymers has a bimodal particle size distribution, without being limited thereto. With the mixture of the acrylate-based rubber polymers, the thermoplastic resin composition can have uniform impact resistance.
In some embodiments, the acrylate-based rubber polymer may be present in an amount of about 20 wt % to about 70 wt %, for example, about 30 wt % to about 60 wt %, based on 100 wt % of the acrylate-based rubber-modified vinyl graft copolymer, and the monomer mixture (including the aromatic vinyl monomer and the vinyl cyanide monomer) may be present in an amount of about 30 wt % to about 80 wt %, for example, about 40 wt % to about 70 wt %, based on 100 wt % of the acrylate-based rubber-modified vinyl graft copolymer. Within these ranges, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, impact resistance, chemical resistance, and the like.
In some embodiments, the aromatic vinyl monomer is a monomer graft-polymerizable with the rubber polymer and may include, for example, styrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, p-t-butylstyrene, ethylstyrene, vinylxylene, monochlorostyrene, dichlorostyrene, dibromostyrene, and vinyl naphthalene, without being limited thereto. These may be used alone or as a mixture thereof. The aromatic vinyl monomer may be present in an amount of about 10 wt % to about 90 wt %, for example, about 40 wt % to about 90 wt %, based on 100 wt % of the monomer mixture. Within this range, the thermoplastic resin composition can exhibit good properties in terms of formability, impact resistance, and the like.
In some embodiments, the vinyl cyanide monomer is copolymerizable with the aromatic vinyl monomer and may include, for example, acrylonitrile, methacrylonitrile, ethacrylonitrile, phenyl acrylonitrile, α-chloroacrylonitrile, fumaronitrile, and the like. These may be used alone or as a mixture thereof. For example, the vinyl cyanide monomer may be acrylonitrile and methacrylonitrile. The vinyl cyanide monomer may be present in an amount of about 10 wt % to about 90 wt %, for example, about 10 wt % to about 60 wt %, based on 100 wt % of the monomer mixture. Within this range, the thermoplastic resin composition can have good properties in terms of chemical resistance, mechanical properties, and the like.
Examples of the monomer for imparting processability and heat resistance may include (meth)acrylic acid, maleic anhydride, and N-substituted maleimide, without being limited thereto. The monomer for imparting processability and heat resistance may be present in an amount of about 15 wt % or less, for example, about 0.1 wt % to about 10 wt %, based on 100 wt % of the monomer mixture. Within this range, the monomer for imparting processability and heat resistance can impart processability and heat resistance to the thermoplastic resin composition without deterioration in other properties.
In some embodiments, the acrylate-based rubber-modified vinyl graft copolymer may be an acrylate-styrene-acrylonitrile graft copolymer (g-ASA), without being limited thereto.
In some embodiments, the acrylate-based rubber-modified vinyl graft copolymer may be present in an amount of about 20 wt % to about 50 wt %, for example, about 25 wt % to about 45 wt %, based on 100 wt % of the thermoplastic resin (including the acrylate-based rubber-modified vinyl graft copolymer and the aromatic vinyl copolymer resin). Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, impact resistance, fluidity (molding processability), external appearance, and balance therebetween.
(A2) Aromatic Vinyl Copolymer Resin
According to the embodiment of the invention, the aromatic vinyl copolymer resin may be an aromatic vinyl copolymer resin used for a typical rubber-modified vinyl copolymer resin. For example, the aromatic vinyl copolymer resin may be a polymer of a monomer mixture comprising an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer, such as a vinyl cyanide monomer.
In some embodiments, the aromatic vinyl copolymer resin may be prepared by mixing the aromatic vinyl monomer and the monomer copolymerizable with the aromatic vinyl monomer, followed by polymerization. Here, polymerization may be carried out by any well-known polymerization method, such as emulsion polymerization, suspension polymerization, bulk polymerization, and the like.
Examples of the aromatic vinyl monomer may include styrene, α-methylstyrene, β-methylstyrene, β-methylstyrene, β-t-butylstyrene, ethylstyrene, vinylxylene, monochlorostyrene, dichlorostyrene, dibromostyrene, and vinyl naphthalene. These may be used alone or as a mixture thereof. The aromatic vinyl monomer may be present in an amount of about 20 wt % to about 90 wt %, for example, about 30 wt % to about 80 wt %, based on 100 wt % of the aromatic vinyl copolymer resin. Within this range, the thermoplastic resin composition can exhibit good properties in terms of impact resistance, fluidity, and the like.
In some embodiments, the monomer copolymerizable with the aromatic vinyl monomer may include, for example, acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, α-chloroacrylonitrile, and fumaronitrile, without being limited thereto. These may be used alone or as a mixture thereof. For example, acrylonitrile, methacrylonitrile, and the like may be used. The monomer copolymerizable with the aromatic vinyl monomer may be present in an amount of about 10 wt % to about 80 wt %, for example, about 20 wt % to about 70 wt %, based on 100 wt % of the aromatic vinyl copolymer resin. Within this range, the thermoplastic resin composition can exhibit good properties in terms of impact resistance, fluidity, and the like.
In some embodiments, the aromatic vinyl copolymer resin may have a weight average molecular weight (Mw) of about 10,000 g/mol to about 300,000 g/mol, for example, about 15,000 g/mol to about 150,000 g/mol, as measured by gel permeation chromatography (GPC). Within this range, the thermoplastic resin exhibits good properties in terms of mechanical strength, formability, and the like.
In some embodiments, the aromatic vinyl copolymer resin may be present in an amount of about 50 wt % to about 80 wt %, for example, about 55 wt % to about 75 wt %, based on 100 wt % of the thermoplastic resin. Within this range, the thermoplastic resin composition can exhibit good properties in terms of impact resistance, fluidity (molding processability), and the like.
(B) UV Stabilizer
The UV stabilizer according to the embodiment of the present invention serves to improve weather resistance, antibacterial properties and the like together with zinc oxide and includes (B1) an HALS (hindered amine light stabilizer)-based UV stabilizer and (B2) a benzotriazole-based UV stabilizer.
(B1) HALS-Based UV Stabilizer
According to one embodiment of the invention, the HALS-based UV stabilizer may include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-2-piperidyl)sebacate, and a combination thereof.
In some embodiments, the HALS-based UV stabilizer may be present in an amount of about 0.05 to about 2 parts by weight, for example, about 0.1 to about 1 part by weight, specifically about 0.2 to about 0.6 parts by weight, relative to 100 parts by weight of the thermoplastic resin. Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, antibacterial properties, and the like.
(B2) Benzotriazole-Based UV Stabilizer
According to one embodiment of the invention, the benzotriazole-based UV stabilizer may include 2-(2H-benzotriazole-2-yl)-4-(1,2,3,3-tetramethylbutyl)phenol, 2-(2-hydroxy-5-methyl-phenyl)benzotriazole, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(5-chloro-2H-benzotriazole-2-yl)-4,6-bis(1,1-dimethylethyl)phenol, and a combination thereof. Preferably, 2-(2H-benzotriazole-2-yl)-4-(1,2,3,3-tetramethylbutyl)phenol is used.
In some embodiments, the benzotriazole-based UV stabilizer may be present in an amount of about 0.05 to about 2 parts by weight, for example, about 0.1 to about 1 part by weight, specifically about 0.1 to about 0.5 parts by weight, relative to about 100 parts by weight of the thermoplastic resin. Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, antibacterial properties, and the like.
In some embodiments, the HALS-based UV stabilizer (B1) and the benzotriazole-based UV stabilizer (B2) may be present in a weight ratio (B1:B2) of about 1:0.5 to about 1:1.1, for example, about 1:0.6 to about 1:1. Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, antibacterial properties, and the like.
(C) Zinc Oxide
According to the present invention, the zinc oxide serves to improve weather resistance and antibacterial properties of the thermoplastic resin composition together with the UV stabilizer, and may have an average particle diameter (D50) of about 0.5 μm to about 3 μm, for example, about 1 μm to about 3 μm, as measured using a particle size analyzer, a BET specific surface area of about 1 m²/g to about 10 m²/g, for example, about 1 m²/g to about 7 m²/g, and a purity of about 99% or higher. Within this range, the thermoplastic resin composition can exhibit good properties in terms of weather resistance, antibacterial properties, and the like.
In some embodiments, the zinc oxide may have a peak intensity ratio (B/A) of about 0 to about 1, for example, about 0.1 to about 1, where A indicates a peak in the wavelength range of 370 nm to 390 nm and B indicates a peak in the wavelength range of 450 nm to 600 nm in photoluminescence measurement. Within this range, the thermoplastic resin composition can have further improved properties in terms of weather resistance, antibacterial properties, and the like.
In some embodiments, the zinc oxide may have a peak position degree (2θ) in the range of 35° to 37° and a crystallite size of about 1,000 Å to about 2,000 Å, for example, about 1,200 Å to about 1,800 Å, in X-ray diffraction (XRD) analysis, as calculated by Scherrer's Equation (Equation 1) with reference to a measured FWHM value (full width at half maximum of a diffraction peak). Within this range, the thermoplastic resin composition can have good properties in terms of initial color, weather resistance, antibacterial properties, and the like.
$\begin{matrix} Crystallite size (D) = \frac{K λ}{β \cos θ} & [Equation 1] \end{matrix}$
where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree), and θ is a peak position degree.
In some embodiments, the zinc oxide may be prepared by melting zinc particles in a reactor, heating the molten zinc to about 850° C. to about 1,000° C., for example, about 900° C. to about 950° C., to vaporize the molten zinc, injecting oxygen gas into the reactor, and cooling the reactor to about 20° C. to about 30° C., followed by heating the reactor to about 700° C. to about 800° C. for about 30 min to about 150 min while injecting nitrogen/hydrogen gas into the reactor, as needed, and cooling the reactor to room temperature (about 20° C. to about 30° C.)
In some embodiments, the zinc oxide may be present in an amount of about 0.1 to about 5 parts by weight, for example, about 0.5 to about 4 parts by weight, relative to about 100 parts by weight of the thermoplastic resin. Within this range, the thermoplastic resin composition can have further improved properties in terms of weather resistance, antibacterial properties, and the like.
In some embodiments, the UV stabilizer (B) and the zinc oxide (C) may be present in a weight ratio (B:C) of about 1:0.5 to about 1:10, for example, about 1:0.6 to about 1:10. Within this range, the thermoplastic resin composition can have further improved properties in terms of weather resistance, antibacterial properties, and the like.
According to one embodiment of the invention, the thermoplastic resin composition may further include additives used in typical thermoplastic resin compositions. Examples of the additives may include a flame retardant, fillers, an antioxidant, an anti-dripping agent, a lubricant, a release agent, a nucleating agent, an antistatic agent, a stabilizer, a pigment, a dye, and a mixture thereof, without being limited thereto. The additives may be present in an amount of about 0.001 to about 40 parts by weight, for example, about 0.1 to about 10 parts by weight, relative to about 100 parts by weight of the thermoplastic resin.
According to one embodiment of the invention, the thermoplastic resin composition may be prepared in pellet form by mixing the aforementioned components, followed by melt extrusion using a typical twin-screw extruder at about 200° C. to about 280° C., for example, about 220° C. to about 250° C.
In some embodiments the thermoplastic resin composition may have a color variation (ΔE) of about 0.5 to about 2.5, for example, about 0.6 to about 1.5, as calculated according to Equation 2 based on initial color values (L₀*, a₀*, b₀*) measured on an injection-molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter and color values (L₁*, a₁*, b₁*) of the specimen measured using the colorimeter after testing for 3,000 hours in accordance with ASTM D4459.
Color variation (ΔE)=√{square root over ((ΔL*)²+(Δa*)²+(Δb*)²)} [Equation 2]
where ΔL* is a difference (L₁*−L₀*) between L* values before and after weather resistance testing, Δa* is a difference (a₁*−a₀*) between a* values before and after weather resistance testing, and Δb* is a difference (b₁*−b₀*) between b* values before and after weather resistance testing.
In some embodiments, the thermoplastic resin composition may have an antibacterial activity of about 2 to about 7, for example, about 4 to about 7, against Staphylococcus aureus and an antibacterial activity of about 2 to about 7, for example, about 3 to 7, against Escherichia coli, as measured on 5 cm×5 cm specimens after inoculation with Staphylococcus aureus and Escherichia coli, respectively, and culturing under conditions of 35° C. and 90% RH for 24 hours, in accordance with JIS Z 2801, and calculated according to Equation 3.
Antibacterial activity=log(M1/M2) [Equation 3]
where M1 is the number of bacteria as measured on a blank specimen after for 24 hours and M2 is the number of bacteria as measured on a specimen of the thermoplastic resin composition after incubation for 24 hours.
A molded article according to the present invention is produced from the thermoplastic resin composition. The thermoplastic resin composition may be prepared in pellet form and the prepared pellets may be produced into various molded articles (products) by various molding methods, such as injection molding, extrusion, vacuum molding, and casting. Such molding methods are well known to those skilled in the art. The molded articles exhibit good properties in terms of weather resistance, antibacterial properties, impact resistance, fluidity (molding processability), and balance therebetween, and thus may be used for interior/exterior materials for electric/electronic products, for example, interior/exterior materials for washing machines, and the like.

MODE FOR INVENTION

Next, the present invention will be described in more detail with reference to some examples. It should be understood that these examples are provided for illustration only and are not to be construed in any way as limiting the invention.

Example

Details of components used in Examples and Comparative Examples are as follows.
(A) Thermoplastic Resin
An acrylate-based rubber-modified vinyl copolymer resin comprising 40 wt % of (A1) an acrylate-based rubber-modified aromatic vinyl graft copolymer and 60 wt % of (A2) an aromatic vinyl copolymer resin was used.
(A1) Acrylate-based rubber-modified aromatic vinyl graft copolymer
A g-ASA copolymer obtained by grafting 55 wt % of a mixture comprising styrene and acrylonitrile (weight ratio: 75/25) to 45 wt % of butyl acrylate rubber having a Z-average particle diameter of 310 nm was used.
(A2) Aromatic Vinyl Copolymer Resin
(A2-1) An SAN resin (weight average molecular weight: 130,000 g/mol) obtained through polymerization of 70 wt % of styrene and 30 wt % of acrylonitrile was used.
(B) UV Stabilizer
(B1) As an HALS-based UV stabilizer, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate was used.
(B2) As a benzotriazole-based UV stabilizer, 2-(2H-benzotriazole-2-yl)-4-(1,2,3,3-tetramethylbutyl)phenol was used.
(B3) 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-hexyloxyl-phenol was used.
(C) Zinc Oxide
(C1) Zinc oxide having an average particle diameter, a BET surface area, a purity, and a peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm in photoluminescence measurement, and a crystallite size as listed in Table 1 was used.
(C2) Zinc oxide having an average particle diameter, a BET surface area, a purity, and a peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm in photoluminescence measurement, and a crystallite size as listed in Table 1 was used.
(C3) Zinc oxide having an average particle diameter, a BET surface area, a purity, and a peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm in photoluminescence measurement, and a crystallite size as listed in Table 1 was used.

TABLE 1

(C1)	(C2)	(C3)

Average particle diameter (μm)	0.6	1.1	1.1
BET surface area (m²/g)	6	40	15
Purity (%)	99	96	99
PL peak intensity ratio (B/A)	0.28	1.17	6.49
Crystallite size (Å)	1,467	141	1,027

Property Measurement
(1) Average particle diameter (unit: μm): Average particle diameter was measured using a particle size analyzer (Laser Diffraction Particle size analyzer LS 13 320, Beckman Coulter Co., Ltd.).
(2) BET surface area (unit: m²/g): BET surface area was measured by a nitrogen gas adsorption method using a BET analyzer (Surface Area and Porosity Analyzer ASAP 2020, Micromeritics Co., Ltd.).
(3) Purity (unit: %): Purity was measured by thermo-gravimetric analysis (TGA) based on the weight of the remaining material at 800° C.
(4) PL peak intensity ratio (B/A): Spectrum emitted upon irradiation of a specimen using a He-Cd laser (KIMMON, 30 mW) at a wavelength of 325 nm at room temperature was detected by a CCD detector in a photoluminescence measurement method, in which the CCD detector was maintained at −70° C. A peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm was measured. Here, an injection molded specimen was irradiated with laser beams without separate treatment upon PL analysis and zinc oxide powder was compressed in a pelletizer having a diameter of 6 mm to prepare a flat specimen.
(5) Crystallite size (unit: Å): Crystallite size was measured using a high-resolution X-ray diffractometer (PRO-MRD, X'pert Co., Ltd.) at a peak position degree (2θ) in the range of 35° to 37° and calculated by Scherrer's Equation (Equation 1) with reference to a measured FWHM value (full width at half maximum of a diffraction peak). Here, both a specimen in powder form and an injection molded specimen could be used, and for more accurate analysis, the injection molded specimen was subjected to heat treatment at 600° C. in air for 2 hours to remove a polymer resin before XRD analysis.
$\begin{matrix} Crystallite size (D) = \frac{K λ}{β \cos θ} & [Equation 2] \end{matrix}$
where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree), and θ is a peak position degree.

Examples 1 to 5 and Comparative Examples 1 to 7

The above components were weighed in amounts as listed in Tables 2 and 3, and subjected to extrusion at 230° C., thereby preparing pellets. Extrusion was performed using a twin-screw extruder (L/D=36, Φ: 45 mm). The prepared pellets were dried at 80° C. for 2 hours or more and injection-molded in a 6 oz. injection molding machine (molding temperature: 230° C., mold temperature: 60° C.), thereby preparing specimens. The prepared specimens were evaluated as to the following properties by the following method, and results are shown in Tables 2 and 3.
Property Evaluation
(1) Weather resistance (color variation (ΔE)): For determination of color variation, initial color values L₀*, a₀* and b₀* were measured on an injection molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter (CM-3700A, KONICA MINOLTA) and was then subjected to weather resistance testing for 3,000 hours in accordance with ASTM D4459, followed by measurement of color values L₁*, a₁* and b₁* of the specimen using the colorimeter. Thereafter, a color variation (ΔE) was calculated according to Equation 2.
Color variation (ΔE)=√{square root over ((ΔL*)²+(Δa*)²+(Δb*)²)} [Equation 2]
where ΔL* is a difference (L₁*−L₀*) between L* values before and after testing, Δa* is a difference (a₁*−a₀*) between a* values before and after testing, and Δb* is a difference (b₁*−b₀*) between b* values before and after testing.
(2) Antibacterial activity: Antibacterial activity was measured on 5 cm×5 cm specimens obtained by inoculation with Staphylococcus aureus and Escherichia coli, respectively, and culturing under conditions of 35° C. and 90% RH for 24 hours, in accordance with JIS Z 2801, and calculated according to Equation 3.
Antibacterial activity=log(M1/M2), [Equation 3]
where M1 is the number of bacteria as measured on a blank specimen after for 24 hours and M2 is the number of bacteria as measured on a specimen of the thermoplastic resin composition after incubation for 24 hours.

	TABLE 2

	Example

	1	2	3	4	5

(A) (parts by weight)

100

(B) (parts by	(B1)	0.5	1	0.1	0.5	0.5
weight)	(B2)	0.3	1	0.1	0.3	0.3
	(B3)	—	—	—	—	—
(C) (parts by	(C1)	2	2	2	4	0.5
weight)	(C2)	—	—	—	—	—
	(C3)	—	—	—	—	—

Color variation (ΔE)	1.22	1.02	1.44	0.98	1.22
Antibacterial activity	6	6	6	6	4
(Staphylococcus aureus)
Antibacterial activity	4	4	4	4	3
(Escherichia coli)

	TABLE 3

	Comparative Example

	1	2	3	4	5	6	7

(A) (parts by weight)

100

(B) (parts by	(B1)	—	0.8	0.5	0.5	0.5	0.5	—
weight)	(B2)	0.8	—	0.3	0.3	0.3	—	0.3
	(B3)	—	—	—	—	—	0.3	0.5
(C) (parts by	(C1)	2	2	—	—	—	2	2
weight)	(C2)	—	—	2	—	—	—	—
	(C3)	—	—	—	2	—	—	—

Color variation (ΔE)	3.2	3.8	1.22	1.24	3.4	3.4	3.6
Antibacterial activity	6	6	1	1	1	6	6
(Staphylococcus aureus)
Antibacterial activity	4	4	1	1	1	4	4
(Escherichia coli)

From the result, it can be seen that the thermoplastic resin composition according to the present invention has good properties in terms of weather resistance, antibacterial properties, and the like.
Conversely, the compositions of Comparative Examples 1 and 2 respectively prepared without using the HALS-based UV stabilizer (B1) and the benzotriazole-based UV stabilizer (B2) suffered from deterioration in weather resistance; the compositions of Comparative Examples 3 and 4 prepared using the zinc oxide (C2) and (C3) instead of the zinc oxide (C1) of the present invention suffered from deterioration in antibacterial properties and the like; and the composition of Comparative Example 5 free from zinc oxide suffered from deterioration in antibacterial properties and weather resistance. In addition, the compositions of Comparative Examples 6 and 7 prepared using the UV stabilizer (B3) instead of the HALS-based UV stabilizer (B1) and the benzotriazole-based UV stabilizer (B2) suffered from deterioration in weather resistance.
It should be understood that various modifications, changes, alterations, and equivalent embodiments can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A thermoplastic resin composition comprising:

a thermoplastic resin comprising an acrylate-based rubber-modified vinyl graft copolymer and an aromatic vinyl copolymer resin;

an ultraviolet (UV) stabilizer comprising an HALS (hindered amine light stabilizer)-based UV stabilizer and a benzotriazole-based UV stabilizer; and

zinc oxide having an average particle diameter of about 0.5 μm to about 3 μm and a BET specific surface area of about 1 m²/g to about 10 m²/g.

2. The thermoplastic resin composition according to claim 1, comprising: about 100 parts by weight of the thermoplastic resin comprising about 20 wt % to about 50 wt % of the acrylate-based rubber-modified vinyl graft copolymer and about 50 wt % to about 80 wt % of the aromatic vinyl copolymer resin; about 0.05 to about 2 parts by weight of the HALS-based UV stabilizer; about 0.05 to about 2 parts by weight of the benzotriazole-based UV stabilizer; and about 0.1 to about 5 parts by weight of the zinc oxide.

3. The thermoplastic resin composition according to claim 1, wherein the acrylate-based rubber-modified vinyl graft copolymer is prepared by graft copolymerization of a monomer mixture comprising an aromatic vinyl monomer and a vinyl cyanide monomer to an acrylate-based rubber polymer.

4. The thermoplastic resin composition according to claim 1, wherein the aromatic vinyl copolymer resin is a polymer of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer.

5. The thermoplastic resin composition according to claim 1, wherein the HALS-based UV stabilizer comprises bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and/or bis(2,2,6,6-tetramethyl-2-piperidyl)sebacate.

6. The thermoplastic resin composition according to claim 1, wherein the benzotriazole-based UV stabilizer comprises 2 (2H-benzotriazole-2-yl)-4-(1,2,3,3-tetramethylbutyl)phenol, 2-(2-hydroxy-5-methyl-phenyl)benzotriazole, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, and/or 2-(5-chloro-2H-benzotriazole-2-yl)-4,6-bis(1,1-dimethylethyl)phenol.

7. The thermoplastic resin composition according to claim 1, wherein the zinc oxide has a peak intensity ratio (B/A) of about 0 to about 1, where A indicates a peak in the wavelength range of 370 nm to 390 nm and B indicates a peak in the wavelength range of 450 nm to 600 nm in photoluminescence measurement.

8. The thermoplastic resin composition according to claim 1, wherein the zinc oxide has a peak position (2θ) in the range of 35° to 37° and a crystallite size of about 1,000 Å to about 2,000 Å, in X-ray diffraction (XRD) analysis, as calculated by Equation 1:

\begin{matrix} Crystallite size (D) = \frac{K λ}{β \cos θ} & [Equation 1] \end{matrix}

where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree) of an X-ray diffraction peak, and θ is a peak position degree.

9. The thermoplastic resin composition according to claim 1, wherein the HALS-based UV stabilizer and the benzotriazole-based UV stabilizer are present in a weight ratio (HALS-based UV stabilizer:benzotriazole-based UV stabilizer) of about 1:0.5 to about 1:1.1.

10. The thermoplastic resin composition according to claim 1, wherein the UV stabilizer and the zinc oxide are present in a weight ratio (UV stabilizer:zinc oxide) of about 1:0.5 to about 1:10.

11. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has a color variation (ΔE) of about 0.5 to about 2.5, as calculated according to Equation 2 based on initial color values (L₀*, a₀*, b₀*) measured on an injection-molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter and color values (L₁*, a₁*, b₁*) of the specimen measured using the colorimeter after testing for 3,000 hours in accordance with ASTM D4459:

Color variation (ΔE)=√{square root over ((ΔL*)²+(Δa*)²+(Δb*)²)}, [Equation 2]

where ΔL* is a difference (L₁*−L₀*) between L* values before and after testing, Δa* is a difference (a₁*−a₀*) between a* values before and after testing, and Δb* is a difference (b₁*−b₀*) between b* values before and after testing.

12. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has an antibacterial activity of about 2 to about 7 against Staphylococcus aureus and an antibacterial activity of about 2 to about 7 against Escherichia coli, as measured on 5 cm×5 cm specimens after inoculation with Staphylococcus aureus and Escherichia coli, respectively, and culturing under conditions of 35° C. and 90% RH for 24 hours in accordance with JIS Z 2801.

13. A molded article formed of the thermoplastic resin composition according to claim 1.